grep

grep, egrep, fgrep: Print lines matching a pattern.

Grep searches the named input FILEs
(or standard input if no files are named)
for lines containing a match to the given PATTERN.
By default, grep prints the matching lines.

       grep [options] PATTERN [FILE...]

Options:

  -i, --ignore-case : Ignore case in both the PATTERN and input files.


Examples:

  grep -i felix * */*